package com.example.thread.threadpool;


import java.util.List;
import java.util.Vector;

//ThreadPool
public class ThreadPool {
    private static ThreadPool instance = null;
    //空闲的线程队列
    private List<Worker> idleThreads;
    //已有的线程总数
    private int threadCounter;
    private boolean isShutDown = false;

    private ThreadPool(){
        this.idleThreads = new Vector(5);
        threadCounter = 0;
    }
    public int getCreatedThreadsCount(){
        return threadCounter;
    }

    //取得线程池的实例
    public  synchronized  static ThreadPool getInstance(){
        if (instance == null){
            instance = new ThreadPool();
        }
        return instance;
    }

    //将线程放入池中
    protected  synchronized void repool(Worker repoolingThread){
        if (!isShutDown){
            idleThreads.add(repoolingThread);
        }else {
            //关闭线程
            repoolingThread.shutDown();

        }
    }

    //停止池中的所有线程
    public synchronized void shutdown(){
        isShutDown = true;
        for (int threadIndex = 0; threadIndex < idleThreads.size(); threadIndex++) {
            Worker idleThread = (Worker)idleThreads.get(threadIndex);
            idleThread.shutDown();

        }
    }

    //执行任务
    public synchronized void start(Runnable target){
        Worker thread = null;
        //如果有空闲线程，则直接使用
        if (idleThreads.size() > 0){
            int lastIndex = idleThreads.size() -1;
            thread =(Worker)idleThreads.get(lastIndex);
            idleThreads.remove(lastIndex);
            //立即执行这个任务
            thread.setTarget(target);
        }else {
            //没有空闲线程，则创建新线程
            threadCounter++;
            //创建新线程
            thread = new Worker(target,"PTread #"+threadCounter,this);
            //启动这个线程
            thread.start();
        }
    }

}
